Two grandchildren were at Leader's side when he died at 5 a.m. at his home at the Country Meadows assisted-living center in Hershey, Kelly S. Kuntz, spokeswoman for Country Meadows, said. The center was the first in a network of 10 such facilities that Leader and his wife founded in 1985.
"Up until two weeks ago he was still going to work," Kuntz said. "Gov. Leader lived a very full, active life."
A Democrat who was the second-youngest person to be elected Pennsylvania governor, Leader fought to rid government of patronage jobs and improve social services. Under his leadership, the state overhauled its mental health system and made special education a requirement in Pennsylvania schools. And, he was the first governor to appoint a black cabinet officer.
Gov. Tom Corbett ordered state flags to be lowered to half-staff until sunset on the day that Leader is buried. Funeral arrangements were incomplete Thursday.
Leader was 37 when he took office as governor in 1955, and he served one four-year term, the maximum allowed by law at the time.
Before that, he succeeded his father, a successful poultry farmer, in the state Senate in 1951 and served until 1954.
Leader ended his political career after losing a bid for U.S. Senate to Republican Hugh Scott in 1958 and spent the following decades running his assisted-living businesses and fighting for causes such as prison reform.
Leader and his wife gave Country Meadows to their children, Kuntz said, but they also founded Providence Place Retirement Communities and the nonprofit Ecumenical Retirement Community in Harrisburg. Leader and his wife, Mary Jane, were living at Country Meadows when she died in March 2011.
Corbett, a Republican, called Leader a friend and said he "defied political labels and conventional thinking in his tireless work for Pennsylvania and its people."
Former Gov. Ed Rendell said Leader will be remembered as "a man who cared very deeply about what happened around him."
"Considering the impact of George Leader on government, politics, community, business and philanthropy, it's fair to say that there's been maybe no Pennsylvanian in our history that has had such a dramatic impact on so many different aspects of our life." Rendell said.
Leader lost his first statewide political campaign when he ran for state treasurer in 1952. He was widely expected to lose the 1954 gubernatorial election, but he used the then-new medium of television to gain a sizable edge over Lt. Gov. Lloyd Wood, a rumpled, cigar-chomping political boss.
He won the election and was the second-youngest governor of Pennsylvania, behind Robert E. Pattison, who was 32 when he was inaugurated in 1883.
One of Leader's biggest accomplishments was cutting the population in Pennsylvania's mental hospitals from 39,000 to 11,000 by giving more state money to mental health clinics that helped patients adjust to life outside hospitals.
Leader, a champion of prison reform as a private citizen later in life, said there were lessons that could be applied to modern times from his experiences in the 1950s.
"The moral to the story is that when I was governor, we had 7,000 people in prison. Today we have 33,000 in state prisons, and we can't keep up," Leader told The Associated Press in a 1996 interview. "We could do the same thing with the prison population that we did with the mental health population."
Leader also signed a law changing Pennsylvania's school code to require the education of the disabled. Within five years, 250,000 more children swelled the enrollment lists in public schools.
In 1995, he began a program to make technology available to every impoverished child in the Harrisburg region through a network of computer instruction courses offered by churches. Leader said giving youngsters opportunities may help them avoid a future behind bars.
Leader belonged to an old York County family, and the village of Leader Heights bears their name.
Leader was born on January 17, 1918, the third of seven children in a Pennsylvania Dutch family. He grew up on his parent's poultry farm and attended a one-room schoolhouse, then York High School and later Gettysburg College.
In 1939, he married Mary Jane Strickler, whom he had dated since high school.
Leader served aboard the aircraft carrier USS Randolph during World War II. When the war ended, he returned to York County and used a GI loan to buy a 110-acre farm.